1. Field of the Invention
The present invention relates to an image forming apparatus such as a photocopier, facsimile machine or printer, and more particularly, to a cleaning device for removing unnecessary adhered substances adhered to the surface of an image carrier, which is a surface moving member, provided in these image forming apparatuses having a cleaning member such as a cleaning blade that removes the adhered substances by contacting the surface moving member, and to a process cartridge provided with this cleaning device.
2. Description of the Related Art
Conventionally, this type of image forming apparatus is frequently provided with a surface moving member such as a photosensitive drum, an image carrier such as an intermediate transfer belt, and a surface transport member such as a recording material conveyor belt that transports a recording material such as paper. In general, since various problems occur if unnecessary adhered substances adhere to the surface of such a surface moving member, cleaning means is required for removing the adhered substances from the surface of the surface moving member. Due to its simple configuration and superior performance in removing adhered substances, a blade-type cleaning device is widely used for this cleaning means, which removes adhered substances from the surface of a surface moving member by pressing a cleaning blade composed of an elastic member such as polyurethane rubber against the surface of the surface moving member.
Known examples of this type of cleaning device of the cleaning blade type include those disclosed in the patent publications indicated below:    Japanese Patent Application Laid-open No. S60-198574,    Japanese Patent Application Laid-open No. 2006-178164,    Japanese Patent Application Laid-open No. 2008-096965, and    Japanese Patent Application Laid-open No. 2008-233319.
More specifically, known examples of cleaning devices of the cleaning blade type include those employing a trailing method as disclosed in the Japanese Patent Application Laid-open No. S60-198574, and those employing a counter method as disclosed in the Japanese Patent Application Laid-open No. 2006-178164. In general, since the counter method is able to increase the contact pressure of the cleaning blade on the surface of the surface moving member as compared with the trailing method, the counter method has the advantage of higher performance in removing adhered substances on the surface of the surface moving member as compared with the trailing method. Thus, in cases requiring a high level of performance in removing adhered substances, a cleaning device of the counter type is employed. In particular, recent image forming apparatuses of the electronic photography type frequently use a spherical toner having a small particle diameter, and particularly a polymer toner, and a high level of removal performance is required to remove these types of adhered substances in the form of toner. Consequently, since cleaning devices of the trailing type have inadequate performance for removing such adhered substances, cleaning devices of the counter type are employed for this purpose.
On the other hand, in a conventional cleaning device of the counter type, if the cleaning blade is pressed against the surface of the surface moving member with an excessively large force to obtain a high level of adhered substance removal performance, the surface moving member and the cleaning blade itself become worn, thereby resulting in the problem of shortening the service life of the surface moving member and the cleaning blade.
In order to solve such problems, a cleaning device disclosed in the Japanese Patent Application Laid-open No. 2008-096965 is known. In this cleaning device, warping of the cleaning blade, which occurs when a cleaning blade that is long in the direction of width of the surface moving member is pressed against the surface of the surface moving member, is restricted by a warping restrict ion member. As a result, the length of a contact portion in the direction of surface movement of the surface moving member between the cleaning blade and the surface of the surface moving member (to be referred to as the “contact width”) can be shortened as compared with a cleaning device in which warping of the cleaning blade is not restricted. Namely, in a conventional cleaning device of the counter type in which warping of the cleaning blade is not restricted, warping of the cleaning blade and deformation of the cleaning blade itself occur as a result of the contact edge of the cleaning blade pressing against the surface of the surface moving member. The contact width becomes longer the greater the warping of the cleaning blade, and also becomes longer the greater the deformation of the cleaning blade itself. In this cleaning device, since warping of the cleaning blade is restricted by a warping restriction member, the contact width is primarily only determined by deformation of the cleaning blade itself. Thus, in this cleaning device, contact width can be shortened in comparison with a conventional cleaning device of the counter type in which warping of the cleaning blade is not restricted. Since wear of the surface moving member and cleaning blade decrease the shorter the contact width for the same contact pressure, in this cleaning device, wear of the surface moving member and cleaning blade can be inhibited as compared with conventional cleaning devices of the counter type in which warping of the cleaning blade is not restricted.
However, in an image forming apparatus, the positional relationship between the surface moving member and the cleaning blade may shift due to production tolerances or member deformation attributable to environmental fluctuations within the image forming apparatus body. In this cleaning device of Japanese Patent Application Laid-open No. 2008-096965, if the positional relationship between the surface moving member and the cleaning blade shifts, there is the risk of being unable to suitably maintain the contact status between the surface moving member and the cleaning blade in the lengthwise direction of the cleaning blade. In the most extreme cases, locations may be formed where contact is not made in the lengthwise direction. In a configuration in which warping of the cleaning blade is not restricted, even if a shift occurs in the above-mentioned positional relationship, the contact status was able to be maintained due to the shift in the positional relationship being absorbed as a result of restoration of warping of the cleaning blade. However, in a configuration in which warping of the cleaning blade is restricted as in this cleaning device, since there is no warping of the cleaning blade, correction of a shift in the positional relationship goes virtually uncorrected even if such a shift occurs. Accordingly, when employing a configuration in which warping of the cleaning blade is restricted as in this cleaning device for the cleaning means of the surface moving member, unless the cleaning device is provided with a configuration that absorbs and corrects any shifts in the above-mentioned positional relationship, the above-mentioned contact status of the contact portion can no longer be maintained over time due a shift in the positional relationship. Consequently, the problem results in which locations occur where cleaning of the surface moving member is not carried out adequately.
Thus, in order to solve such problems, in a cleaning device disclosed in the Japanese Patent Application Laid-open No. 2008-233319, engaged means provided in a retaining member that retains a cleaning blade in the manner described above, and engaging means supported by the device body, engage such that a gap is formed between the engaging means and the engaged means when in an engaged state. Due to the presence of this gap, the engaging means and the engaged means engage with a degree of freedom, and the retaining member can be displaced relative to the device body. As a result, shifts in the positional relationships between each member due to production tolerances or environmental fluctuations can be corrected by displacement of the retaining member relative to the device body, thereby making it possible to maintain contact between the surface moving member and the cleaning blade. Thus, the occurrence of uneven contact in the lengthwise direction of the cleaning blade can be inhibited, and the contact status between the cleaning blade and the surface of the surface moving member to be maintained over time.
However, in the case of a configuration like that of a cleaning device described in the above-mentioned prior application in which a gap is formed between engaged means of a retaining member and engaging means on the device body when in an engaged state, if foreign objects such as toner or lubricant become entrapped in the gap, there is the risk of the effectiveness of the gap being lost. Namely, the degree of freedom in engagement between the engaging means and the engaged means obtained due to the presence of the gap is lost, the retaining member is no longer able to be displaced relative to the device body, or production tolerances or shifts in positional relationships can no longer be corrected, thereby resulting in the risk of being unable to inhibit the occurrence of uneven contact in the lengthwise direction of the cleaning blade.